This invention relates to starters in general and more particularly to a starter suitable for use in starting an internal combustion engine of an automotive vehicle.
A starter of the so-called cantilever pinion type includes a one-way clutch having an inner member and an outer member, the outer member being threadably connected to an output shaft of an electric motor driven by a rotor and the inner member being formed integrally with a hollow pinion shaft and slidably fitted in the output shaft of the electric motor, and a fixed frame supporting the outer periphery of the hollow pinion shaft by means of a bearing. This starter of the prior art has, as is well known from U.S. Pat. No. 3,171,284, been in use as a dust preventing type starter for various types of engines. This type of starter has a mechanism which best suits the condition of a dust preventing type starter, but its disadvantage is that since the hollow pinion shaft and the inner member of the clutch are formed integrally, the reaction produced in the pinion when the engine is started is transmitted to the inner member of the clutch, tending to cause tilting of the inner member. When this phenomenon happens, the inner member of the clutch becomes eccentric relative to the outer member thereof and the action of the clutch becomes unstable, so that the clutch is unable to function satisfactorily. In this type of starter, the hollow pinion shaft has an outer diameter greater than that of the pinion for facilitating assembling of the starter (generally, after the clutch is assembled, the clutch is fitted in the output shaft of the electric motor, and the output shaft is then inserted in the bearing from inside the fixed frame to be supported by the bearing). This necessarily results in the bearing having a larger inner diameter, causing an increase in the peripheral velocity of the pinion shaft and a loss of torque of the electric motor.
Meanwhile proposals have hitherto been made to adopt a construction in which the pinion is provided separately from the hollow pinion shaft to reduce the peripheral velocity of the pinion shaft or reduce the inner diameter of the bearing, so that the pinion will be attached to the pinion shaft after the starter is assembled. However, this construction is not successful when the pinion has a small root diameter because such pinion does not have sufficiently high strength.